forked from Minki/linux
ARM: initial stack protector (-fstack-protector) support
This is the very basic stuff without the changing canary upon task switch yet. Just the Kconfig option and a constant canary value initialized at boot time. Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
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@ -1374,6 +1374,18 @@ config UACCESS_WITH_MEMCPY
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However, if the CPU data cache is using a write-allocate mode,
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this option is unlikely to provide any performance gain.
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config CC_STACKPROTECTOR
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bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
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help
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This option turns on the -fstack-protector GCC feature. This
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feature puts, at the beginning of functions, a canary value on
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the stack just before the return address, and validates
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the value just before actually returning. Stack based buffer
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overflows (that need to overwrite this return address) now also
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overwrite the canary, which gets detected and the attack is then
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neutralized via a kernel panic.
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This feature requires gcc version 4.2 or above.
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endmenu
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menu "Boot options"
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@ -34,6 +34,10 @@ ifeq ($(CONFIG_FRAME_POINTER),y)
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KBUILD_CFLAGS +=-fno-omit-frame-pointer -mapcs -mno-sched-prolog
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endif
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ifeq ($(CONFIG_CC_STACKPROTECTOR),y)
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KBUILD_CFLAGS +=-fstack-protector
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endif
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ifeq ($(CONFIG_CPU_BIG_ENDIAN),y)
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KBUILD_CPPFLAGS += -mbig-endian
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AS += -EB
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38
arch/arm/include/asm/stackprotector.h
Normal file
38
arch/arm/include/asm/stackprotector.h
Normal file
@ -0,0 +1,38 @@
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/*
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* GCC stack protector support.
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*
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* Stack protector works by putting predefined pattern at the start of
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* the stack frame and verifying that it hasn't been overwritten when
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* returning from the function. The pattern is called stack canary
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* and gcc expects it to be defined by a global variable called
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* "__stack_chk_guard" on ARM. This unfortunately means that on SMP
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* we cannot have a different canary value per task.
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*/
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#ifndef _ASM_STACKPROTECTOR_H
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#define _ASM_STACKPROTECTOR_H 1
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#include <linux/random.h>
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#include <linux/version.h>
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extern unsigned long __stack_chk_guard;
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/*
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* Initialize the stackprotector canary value.
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*
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* NOTE: this must only be called from functions that never return,
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* and it must always be inlined.
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*/
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static __always_inline void boot_init_stack_canary(void)
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{
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unsigned long canary;
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/* Try to get a semi random initial value. */
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get_random_bytes(&canary, sizeof(canary));
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canary ^= LINUX_VERSION_CODE;
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current->stack_canary = canary;
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__stack_chk_guard = current->stack_canary;
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}
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#endif /* _ASM_STACKPROTECTOR_H */
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@ -37,6 +37,12 @@
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#include <asm/stacktrace.h>
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#include <asm/mach/time.h>
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#ifdef CONFIG_CC_STACKPROTECTOR
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#include <linux/stackprotector.h>
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unsigned long __stack_chk_guard __read_mostly;
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EXPORT_SYMBOL(__stack_chk_guard);
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#endif
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static const char *processor_modes[] = {
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"USER_26", "FIQ_26" , "IRQ_26" , "SVC_26" , "UK4_26" , "UK5_26" , "UK6_26" , "UK7_26" ,
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"UK8_26" , "UK9_26" , "UK10_26", "UK11_26", "UK12_26", "UK13_26", "UK14_26", "UK15_26",
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